This invention relates to broad spectrum .beta.-lactam antibiotic compounds. In particular, it relates to bicyclic 1-oxa-.beta.-lactam compounds substituted in the 3-position with a bis-tetrazolmethyl thiomethyl substituent represented by the following general formula wherein the positions in the molecule are numbered as shown. ##STR2## In the above formula, R represents the residue of a carboxylic acid, R.sub.2 represents hydrogen or methoxy, and R.sub.4 represents hydrogen or C.sub.1 -C.sub.3 alkyl.
1-Oxa-.beta.-lactam compounds are known, for example, those described in Belgium Pat. No. 863,998 issued May 29, 1978, and those described by Narisada et al., in U.S. Pat. No. 4,138,486, issued Feb. 6, 1979. In paricular, Narisada et al. describe 1-oxa-.beta.-lactam compounds substituted in the 3-position with a 1-methyl-1H-tetrazol-5-yl-thiomethyl substituent, and in the 7-position with a phenylmalonamido substituent or an hydroxy or acyloxy substituted phenylmalonamido substituent. These 1-oxa-.beta.-lactam compounds have high antibacterial activity and have stimulated numerous workers to carry out the synthesis of new members of the class with improved biological activity.
The compounds of this invention as represented by the above general formula differ structurally from those described by Narisada et al. U.S. Pat. No. 4,138,466, and in Belgium Pat. No. 863,998.